hw2_solutions

hw2_solutions - Homework #2: Solutions Astro 10, spring...

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Homework #2: Solutions Astro 10, spring 2010 General Notes to Graders: If numerical answers are roughly correct, do not take marks off. Award part marks if the student has made some progress with the question. 1. [5 points] Adaptive optics is a means of correcting for the distortion induced in optical images by disturbances in the atmosphere . Without the system, the resolution of large optical telescopes doesn’t improve past about 5m mirror size because currents in the atmosphere will refract the light before it reaches the mirror. Thus, you do not get the full benefit of all the resolution your telescope is capable of. Incidentally, this is the same mechanism that causes stars to twinkle when you look at them. Adaptive optics shines a laser into the atmosphere or uses a close by bright star to measure the distortions of the atmosphere , and then adjusts a deformable mirror to compensate using computer control. The system is installed at the Keck telescope in Hawaii, where the resolution now rivals the Hubble Space telescope. Notes to graders: Students should have a discussion equivalent to this in content to receive full credit. 2. [5 points] The key to determining composition is the pattern of absorption or emission lines imprinted on the continuous blackbody background . As you saw in lecture and in section, the pattern of emission/absorption lines is unique to each atom, ion and molecule . By matching the observed lines with known lines from a particular substance, an astronomer can deduce the composition of the observed object (such as a star, a cloud of gas, a galaxy, etc. ..). Notes to graders: Students should have a discussion equivalent to this in content to receive full credit. 3. [5 points] You can’t say anything about the distance between the two stars , because you haven’t mea- sured the distance to them. All you know is their angular separation . For all you know, one star could be 1 lightyear (ly) away, while the other is at 5 ly. Or they could be equidistant. Without
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This note was uploaded on 07/18/2011 for the course ASTRO 10 taught by Professor Norm during the Spring '06 term at Berkeley.

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hw2_solutions - Homework #2: Solutions Astro 10, spring...

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